Sockets are used widely in the electronics industry to mount and connect microelectronic devices such as semiconductor integrated circuits (“ICs”) to electronics systems of various sorts—as is well known, a socket is used to connect terminals on a device to corresponding contacts on a printed circuit board or other electrical interconnection means. In addition, sockets are routinely used in systems for: (a) testing electronic device performance (an assortment of socket types have been developed to connect to a device under test (“DUT”) having a wide variety of terminals and configurations), or (b) bum-in of electronic devices at elevated temperatures.
Prior art sockets are differentiated typically according to device terminals and intended end use (i.e., application). As such, sockets are typically designed to make electrical contact to microelectronic devices having specific types of device terminals—types of device terminals contacted by sockets include pin grid arrays (“PGAs”), J-leads, gull-wing leads, dual in-line (“DIP”) leads, ball grid arrays (“BGAs”), column grid arrays (“CGAs”), flat metal pads (“LAN” grid arrays or “LGAs”), and many others. In order to provide sockets for microelectronic devices with this variety of terminals, many contactor technologies have been developed for sockets. In addition to the foregoing, further differentiation among prior art sockets refers to low insertion force (“LIF”) sockets, zero insertion force (“ZIF”) sockets, auto-load sockets, bum-in sockets, high performance test sockets, and production sockets (i.e., sockets for use in products). In further addition to the foregoing, low cost prior art sockets for bum-in and product applications typically incorporate contactors of stamped and formed springs to contact terminals on a DUT. In still further addition to the foregoing, for high pin-count prior art sockets, a cam is often used to urge device terminals laterally against corresponding contactors to make good contact to each spring while allowing a low or zero insertion force.
For specialized applications, prior art sockets have used a wide variety of contactors, including anisotropic conductive sheets, flat springs, lithographically formed springs, fuzz buttons (available from Cinch, Inc. of Lombard, Ill.), spring wires, barrel connectors, twisted wire springs in an elastomer, and spring forks, among others. Prior art sockets intended for applications where many test mating cycles (also referred to as socket mount-demount cycles) are required typically use spring pin contactors of the type exemplified by Pogo® spring contacts (available from Everett Charles Technologies of Pomona, Calif.). Spring probes for applications in the electronics test industry are available in many configurations, including simple pins and coaxially grounded pins. Most prior art spring probes consist of a helical wire spring disposed between a top post (for contacting terminals on the DUT) and a bottom post (for contacting contacts on a circuit board—a device under test board or “DUT board”).
Prior art sockets typically consist of a plurality of contactors disposed in an array of apertures formed through a dielectric holder. By way of example, a high performance, prior art test socket may incorporate a plurality of Pogo® spring contacts, each of which is held in a pin holder consisting of an array of holes through a thin dielectric plate. The dielectric material in a high performance, prior art test socket is typically selected from a group of dimensionally stable polymer materials including: glass reinforced Torlon 5530 available from Quadrant Engineering Plastic Products, Inc. of Reading, Pa.; Vespel; Ultem 2000 available from GE Company GE Plastics of Pittsfield, Mass.; PEEK; liquid crystal polymer; and others. The individual Pogo® spring contacts are typically selected and designed for signal conduction at an impedance level of approximately fifty (50) ohms. In certain high performance, prior art configurations, the contactor is a coaxial type having a center spring pin with a contactor barrel body enclosed within a cylindrical, coaxial, ground shield spaced to achieve a desired signal impedance, typically fifty (50) ohms.
Materials other than dielectric sheets have been used for prior art socket bodies. For example, ceramic materials including alumina, aluminum nitride, and low temperature co-fired ceramic are used for high temperatures. In addition, insulation coated, metal socket bodies have been used to control dimensional stability over a range of temperature. In further addition, laminated bodies of alternating layers of dielectric and metal materials in thermal contact with elastomeric contactors and compliant contactors have been used.
As is well known to those of ordinary skill in the art, a primary function of prior art sockets is to provide reliable and repeatable electrical contact to microelectronic device terminals (i.e., a capability to mount and demount a device on the socket repeatedly, without causing damage to either). As such, a measure of quality is contact resistance between device terminals and corresponding contacts on a measurement system, determined as a function of a number of repeated mating cycles. For example, a high performance socket will typically provide a contact resistance of 20 milliohms or less for 10,000 mating cycles. More recently, advances in semiconductor devices are placing additional demands on IC sockets. In particular, increasing power and current levels require sockets that can supply more current per terminal. Further, at higher levels of current, the socket becomes a source of heat due to current flowing through the contact resistance of each pin. Further demands are also placed on the socket for signal performance relating to: (a) controlled impedance for signal terminals; (b) low cross talk between signal terminals; and (c) low inductance power and ground connections to a device.
In light of the above, despite the many socket technologies available in the prior art, there is a need in the art for a socket that can satisfy one or more of the above-identified demands relating to high current, low impedance power and ground connections, impedance control, and isolation of high frequency signal terminals.